In the Third Generation Partnership Project (3GPP) standard Rel. 13, one-to-one HARQ feedback is applied to a Half-Duplex (HD) Machine-To-machine Communication (MTC) system. That is, with respect to data received in each downlink subframe, such as a Physical Downlink Data Channel (PDSCH), HARQ feedback information for the data, for example, positive acknowledgment information (ACK) indicating that the data has been successfully received or negative acknowledgment information (NACK) indicating that the data has not been successfully received, is transmitted by a User Equipment (UE) in a subframe at a predetermined time after the subframe. However, in the half-duplex system, a subframe to be used for transmitting uplink HARQ feedback information may be allocated for downlink transmission, thus resulting in a conflict between the transmission of uplink feedback information and the transmission of downlink data. HARQ bundling is proposed in Rel. 14 to solve this problem, in which HARQ feedback information for a plurality of received data is bundled together and transmitted to a base station by the UE. For example, the UE performs a logical addition operation on the plurality of received data and transmits the calculation result as feedback information to the base station.
In a Rel. 14 based HD TDD MTC system, a downlink subframe on which HARQ bundling should be performed and an uplink subframe used for transmitting feedback information in the case that HARQ bundling is applied are specified for each downlink-uplink configuration. However, how to perform HARQ bundling is not discussed in the Rel. 14 based HD TDD MTC system.
Therefore, a method for performing HARQ bundling in a Rel. 14 based HD TDD MTC system is needed.